In manufacturing an LCD device, liquid crystals are injected in a sealed space confined by two substrates to form a liquid crystal layer that generally permits light beams to pass therethrough in a normal state. The liquid crystals are normally in a liquid state rather than a solid state. Since they are very sensitive to heat, their orientation changes when an appropriate voltage is applied thereto so as to control light passage, thereby converting the liquid crystal layer into non-transparent or half-transparent state, which consequently results in an image display. Generally, an alignment layer is fabricated on the glass substrate by the photo printing technique in order to set the pre-tilt angles of the orientation of the liquid crystal molecules in the liquid crystal layer. The alignment layer can be made from natural polymer or artificial polymer (polymide), which may have to be treated in advance by photolithographic masking and rubbing operations in order to manipulate the orientation of nearby liquid crystal molecules. Prior to assembly, the substrate (with the alignment layer thereon) must undergo several testing and checking operations so that its defect can be found and/or the orientation of the substrate can be determined.
Typically, testing and checking operations of the glass substrate 1 are accomplished manually as shown in FIG. 1. The glass substrate 1 is held by one person, and is passed adjacent to a steam-generating device 31 in such a manner to form a plurality of water drops or water layer 32 on the alignment layer 10 by virtue of its initial low temperature. A light projector 22 is then used to direct light beams onto the alignment layer 10. In order to determine the orientation of the alignment layer 10 and/or find out the defects of the alignment layer 10, the reflection and refraction of light caused by the water drops hanging on the alignment layer 10 are observed by naked eyes of a tester 4 by changing several viewing angles with respect to the glass substrate 1.
Some drawbacks of the above testing method are as follow:
(ii) The resultant orientation of the alignment layer is not uniform because the procedure of determining orientation of the alignment layer is unduly depends on different personal experience and skills of an operator.
(iii) Several defected alignment layers must be discarded, thereby increasing the cost of manufacture.